1. Field of the Invention
The present invention, in general, relates to lifting and lowering heavy objects and, more particularly, to a device for lifting and lowering tree limbs.
Trees sometimes require the removal of troublesome limbs that pose a threat to property disposed below the limbs. Sometimes, an entire tree will require removal for a wide range of possible reasons. Sometimes, the mere positioning of the tree can pose a threat to people or pets, livestock, personal property, power, cable, or telephone lines, commercial or residential property or interests, traffic, adjoining property, etc. Sometimes, insects, lightning strikes, fire, or disease will have weakened the tree to the point of instability. Sometimes, the tree will need to be removed to facilitate access to an area or for purely aesthetic reasons. These, and numerous other reasons, require the removal of trees and tree limbs.
In developed areas it is usually not feasible or safe to simple cut and fell the tree because it may fall in an undesirable or unpredictable manner and cause property damage or even loss of life. Often, there is simply no space available to permit a normal felling of the tree. In such a situation an arborist or commercial tree service is usually contracted to safely remove the tree or certain of its limbs. For the purpose of consistency, the term “arborist”, as used herein, refers to anyone having knowledge in the tree maintenance and/or tree or limb removal art, including any of the crew that may be employed by the various commercial tree service companies.
It is common practice for the arborist to prune and remove unwanted tree limbs as well as to remove unwanted trees. This work is often performed in tight quarters and with limited access. If possible, a vehicle with equipment is brought into the area.
The removal process is typically accomplished by a process that is well known in the arbor field. A block and tackle is employed with a pulley of the block and tackle firmly anchored to an overhead limb of the tree that is to have certain of its limbs removed and, possibly, to have the entire tree removed. The use of a block and tackle is done to provide a way to control the rate of descent of each limb that is severed. It may also provide a mechanical advantage. If a hoist is available (sometimes called a “cherry picker”) it is used to elevate the worker safely to the overhead limb. The worker then secures the pulley to the overhead limb. A rope is used as part of the block and tackle. The rope passes over the pulley.
The worker then secures an upper first end of the rope to the limb that is to be severed. The rope is commonly set to pass around a circumference of the limb and is secured to itself by use of a knot, if desired. Another common way of securing the rope in a tightened (or desired position) is by use of a device intended for that purpose. The device, which is well known in the arbor art, may be secured where desired at a location that is near the first end of the rope. The first end of the rope passes through the device.
The device allows tightening of the rope by pulling the first end through the device. The device includes a pivoting member that pivots in a first direction when pulling the rope in a first direction through the device that allows for easy passage of the rope through the device. When the worker releases tension on the first end of the rope, the rope is urged through by the force exerted from the load in a second direction through the device that is opposite that of the first direction through the device.
Motion by the rope in the second direction bears on the pivoting member and urges the pivoting member in an opposite second direction that causes the pivoting member to increasingly bear upon the rope and bind (i.e., pinch) the rope to the device. Frictional engagement between the rope and the pivoting member and interior of the device ensure that the rope will remain secured at approximately the same position it was located when the worker released pressure from the first end of the rope.
The device allows the rope to easily pass through the device in the first direction and prevents its passing in the second direction. The device provides a safe, secure, and rapid way to tighten the rope around the limb. A manual release on the device allows the rope to pass through the device in the second direction, when desired.
Other methods of securing the first end of the rope to the limb are also available to the arborist. For example, the first end of the rope may be secured to a cable that extends around the limb. The cable is configured to include two loops at opposite ends, thereof. A first of the two loops is allowed to pass around the circumference of the limb and through the opposite second loop. The first end of the rope is then affixed to the first loop by a snap ring or other fastening device or method.
As the weight of the limb bears on cable and the rope, the first loop is increasingly pulled through the second loop, thereby causing the cable to self-tighten around the limb. This provides a secure attachment of the limb to the rope.
Typically, an attempt is made by the worker to secure first end of the rope to the limb at a location that is believed to be near a center of gravity of the limb. This is accomplished to prevent an excessive rotational force from occurring that would otherwise pivot the limb, after its severing, into a more vertical position. Supporting the severed limb proximate its center of gravity provides better control for controlling the position of the limb during its descent.
Before cutting the limb, a lower second end of the rope that descends to the ground is secured and excessive slack in the rope is removed. Typically, for safety reasons, a first ground operator will stand at a remote location that is sufficiently offset from a plumb line extending down from the limb. Standing at the remote location prevents injury from occurring to the first ground operator in the unlikely event that the limb should fall suddenly to the ground.
From the remote location the first ground operator is also better able to observe and control the limb during its descent. At times, a second ground operator is used to displace the limb away from plumb (i.e., as in a plumb line) as it is being lowered. The second ground operator uses additional ropes or long poles to urge the limb in the desired direction of offset from plumb as it is being lowered. The second ground operator does not stand directly under the limb although the second ground operator may stand closer to plumb than does the first ground operator. This is discussed in greater detail below.
From the remote location, the first ground operator is better able to observe the actions of the second ground operator during descent of the limb and comply with instructions that are provided by the second ground operator.
Often, the limb may weigh several hundreds of pounds or even more. If the rope passes once over a single pulley, as is common, the force exerted on the rope by the weight of the limb cannot be offset by the weight or strength of the first ground operator. Therefore, some method must be provided to allow the first ground operator to control the limb's rate of decent.
Many devices have been provided to satisfy this need, some of which include winches or other devices intended to supply a mechanical advantage. However, such solutions tend to be expensive to purchase and they are also time consuming to set up prior to use. They also must be anchored to an object that is sufficiently strong and heavy so as to be to be able to compensate for the weight of the limb. Also, these types of prior art devices typically operate very slowly and this can impede progress in circumstances where a number of limbs can be safely lowered at a higher rate of speed.
Other, more simple devices intended to assist the first ground operator in the safe and controlled lowering of the limb rely on wrapping the rope repeatedly around a spool, adjacent tree, or object as a means of applying and controlling friction between the rope and device, tree, or object. However, these types of devices do not permit lifting of the limb which is sometimes required. This is further discussed below.
As briefly mentioned above, sometimes it is undesirable to allow the limb to descend straight down. It is necessary to offset a descending limb from plumb when an important or fragile object that is difficult or impossible to remove is located below the limb that is to be severed. As mentioned, secondary ropes, poles, or other devices intended to deflect the path of descent are used to guide the descending limb to a location that is offset with respect to plumb.
Sometimes, during descent it becomes apparent that the current degree of deflection experienced by limb will be insufficient. When this occurs it becomes necessary to again raise the limb to a higher elevation and repeat the descent process while applying a different amount of deflection to the limb.
If a prior art type of friction-based limb lowering device is used then it is not possible to raise the limb.
Also, there is a need to be able to secure a limb lowering device quickly and at various anchor points around the tree. This would provide the ground operator with an ability to stand at various locations during lowering of different limbs with each location having a particular advantage. However, prior art devices have been difficult and time-consuming to secure to a location and the number of locations available for anchoring the prior art devices have been severely limited.
Accordingly, there exists today a need for a lifting and lowering device and system that helps to ameliorate the above-mentioned problems and difficulties as well as ameliorate those additional problems and difficulties as may be recited in the “OBJECTS AND SUMMARY OF THE INVENTION” or discussed elsewhere in the specification or which may otherwise exist or occur and that are not specifically mentioned herein.
Clearly, such an apparatus and system would be useful and desirable.
2. Description of Prior Art
Limb lowering devices are, in general, known. For example, the following patents describe various types of these devices, some of which may have relevance as well as others which may not have particular relevance to the invention. These patents are cited not as an admission of their having any particular relevance to the invention but rather to present a broad and diversified understanding regarding the current state of the art appertaining to either the field of the invention or possibly to other related or distal fields of invention.    U.S. Pat. No. 7,007,927 to Halas, that issued on Mar. 7, 2006;    U.S. Pat. No. 6,631,885 to Halas, that issued on Oct. 14, 2003;    U.S. Pat. No. 6,578,823 to Johnson, that issued on Jun. 17, 2003;    U.S. Pat. No. 5,971,363 to Good, that issued on Oct. 26, 1999;    U.S. Pat. No. 5,484,253 to Johnson, that issued on Jan. 16, 1996;    U.S. Pat. No. 5,467,845 to Scruggs, that issued on Nov. 21, 1995;    U.S. Pat. No. 5,395,284 to Frisk, that issued on Mar. 7, 1995;    U.S. Pat. No. 5,352,172 to Suzaki, that issued on Oct. 4, 1994;    U.S. Pat. No. 4,899,680 to Russell, Jr., that issued on Feb. 13, 1990;    U.S. Pat. No. 4,314,693 to Hobbs, that issued on Feb. 9, 1982;    U.S. Pat. No. 4,239,188 to Hobbs, that issued on Dec. 16, 1980;    U.S. Pat. No. 3,116,049 to Stranahan, that issued on Dec. 31, 1963;    U.S. Pat. No. 2,441,336 to Sova, that issued on May 11, 1948;    U.S. Pat. No. 2,235,302 to Stillwagon, that issued on Mar. 18, 1941; and    U.S. Pat. No. 904,747 to Anderson, that issued on Nov. 24, 1908.
While the structural arrangements of the above described devices may, at first appearance, have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices.